Michael Jackson's perfectionism fails him in This Is It, and we're all the better for it. What we see in this unmissable two-hour concert film, culled from 120 hours of digital-video footage of Jackson rehearsing for a promised comeback that ended with his death at age 50 on June 25th, is a world-class performer trying to make the MJ on stage match the MJ in his head. Watching his struggle is illuminating, unnerving and unforgettable.

During prep time from March to June of this year, director Kenny Ortega caters to the every whim of his fragile, passive-aggressive star, knowing instinctively that yelling will only produce pouting not results. This Is It, a so-called "gift" to the fans, will disappoint anyone looking to scrutinize the scandals and facial scars that made the King of Pop a tabloid staple. Among the film's problems, exploitation for starters, are interviews with the singers, dancers and crew gathered like family around Jackson at the Staples Center in Los Angeles. Their words start at worshipful and burst into a Niagara of gush. And the editing of the rehearsals into a semi-cohesive whole emphasizes the big finish over the slow build. But the Jackson onscreen is still an indisputable phenomenon.

Ortega shows us huge chunks of filmed set pieces intended for the epic concert of greatest hits that was set to open in London for 50 performances. On black-and-white celluloid for the "Smooth Criminal" number, we see zoot-suited Jackson machine-gunning it out with Bogart and catching a satin glove thrown by sexy Rita Hayworth in Gilda. "Thriller" gets the Halloween treatment with drooling graveyard ghouls, and computer wizardry turns 11 dancers into a robot army of thousands. In the godawful "Earth Song," a bulldozer decimates a forest on screen and then rolls out on stage to toss the message right in our laps. It's all shameless razzle dazzle aimed at the cheap seats.

Where This Is It triumphs is when it has the sense to keep it simple. Yes, Jackson holds back on the vocals. "Don't make me sing full out," he pleads to the crew, cheering him on in rehearsal as he duets with Judith Hill on "I Just Can't Stop Loving You." He needs to conserve his voice for the actual performance. But the slight rasp adds emotion and warmth to "Human Nature," "Man in the Mirror" and "Billie Jean" — a vulnerability rare in Jackson, who rivaled Fred Astaire in the surgical precision of his presentation. The soundtrack CD for This Is It uses the remastered original recordings, not the live versions, and I can see why. Without the visuals, the vocal flaws might seem glaring. But Jackson just going through the motions puts other performers to shame. And, oh, could that man move. The editing gives us Jackson performing the same number on different days in different clothes. But the film still feels vital and thrillingly alive. In this transcendent tribute to a performing artist flying without a safety net, death holds no sway over Michael Jackson. His soul is still dancing.